Sulfonated polyaniline (SPAN) is a self-doped conducting polymer. It has a high water solubility and a novel pH-dependent DC conductivity that is of interest for fundamental science and also for applications in such areas as rechargeable battery and pH control technologies. We report here the extensive characterization and details of synthesis of a new form of sulfonated polyaniline (LEB-SPAN) which shows novel or significantly improved chemical and physical properties. LEB-SPAN has a high sulfur to nitrogen ratio (S/N) of ∼0.75, 50% larger than that previously reported for EB-SPAN, S/N ∼0.50. This change in composition leads to significant alteration of the properties including an order of magnitude increase in the room temperature DC conductivity to ∼1 S·cm-1, nearly double the solubility in water, and a completely different pH dependence of the oxidation potential (E 1/2). For LEB-SPAN the DC conductivity is unaffected by pH over the range 0 ≤ pH ≤ 14, strikingly different from the behavior of both parent polyaniline and EB-SPAN which become insulating for pH ≥3 and ≥7.5, respectively. Temperature-dependent DC conductivity and EPR measurements for LEB-SPAN reveal a lower activation energy for the conductivity and a higher density of states at the Fermi energy as compared with EB-SPAN. The dramatic differences in the pH dependence of the DC conductivity, cyclic voltammetry (CV), FTIR, and UV−vis results for LEB-SPAN and EB-SPAN are shown to be a consequence of the much higher S/N ratio in LEB-SPAN. We propose and describe a novel quasi-random oxidation model for the electrochemical oxidation of polyaniline and its derivatives at the microscopic level. This model quantitatively describes many of the phenomena and physical properties found in the polyanilines including the origin of the defect states and the in situ EPR signal during CV potential scans. Also the statistical nature of this model suggests its general applicability to the oxidation process of other conducting polymers. Computer simulations based on this model are presented and show good agreement with the in situ EPR/CV data reported earlier. In addition, other models are proposed to interpret the reported experimental differences in the pH dependence of E 1/2 among LEB-SPAN, EB-SPAN, and its parent polyaniline samples. Mechanisms for the new sulfonation route are proposed.

There is a great desire to develop the high-efficient anodes materials for Li batteries, which require not only large capacity but also high stability and mobility. In this work, the phosphorene/graphene heterostructure (P/G) was carefully explored based on first-principles calculations. The binding energy of Li on the pristine phosphorene is relatively weak (within 1.9 eV), whereas the phosphorene/graphene heterostructure (P/G) can greatly improve the binding energy (2.6 eV) without affecting the high mobility of Li within the layers. The electronic structures show that the large Li adsorption energy and fast diffusion ability of the P/G origin from the interfacial synergy effect. Interestingly, the P/G also displays ultrahigh stiffness (Cac = 350 N/m, Czz = 464 N/m), which can effectively avoid the distortion of the pristine phosphorene after the insertion of lithium. Thus, P/G can greatly enhance the cycle life of the battery. Owing to the high capacity, good conductivity, excellent Li mobility, and ultrahigh stiffness, P/G is a very promising anode material in Li-ion batteries (LIBs).

Using a structural search method in combination with first-principles calculations, we found lots of low energy 2D carbon allotropes and examined all possible Dirac points around their Fermi levels. Three amazing 2D Dirac carbon allotropes have been discovered, named as S-graphene, D-graphene and E-graphene. By analyzing the topology correlations among S-, T, net W graphene and graphene, we found that a general rule is valuable for constructing 2D carbon allotropes that are keen to possess Dirac cones in their electronic structures. Based on this rule, we have successfully designed many new 2D carbon allotropes possessing Dirac cones. Their energy order can be well described by an Ising-like model, and some allotropes are energetically more stable than those recently reported. The related electronic structures of these Dirac allotropes are anisotropy distinguished from those of graphene. Moreover, the fact that D- and E-graphene present Dirac cones suggests that sp hybridization or sp(3) hybridization could not suppress the emerging of Dirac features. Our results demonstrate that the Dirac cone and carrier linear dispersion is a very common feature in 2D carbon allotropes and can exist beyond the limitations of fundamental structure features of graphene.

Transition metal chalcogenides have attracted considerable attention for the further development of nanoscale devices, however low carrier mobility seriously prevents its further application.